These are a combination of fission and fusion. (thermal part form fission and nuclear from fusion)
In hydrogen bombs the first step is to make U-235 or Pl-239 undergo fission.
The resultant heat is used to fuse heavy hydrogen atoms (both deuterium and tritium). That’s why it is called thermo-nuclear.
The fusion of deuterium and tritium release energy and neutrons. These neutrons are inturn bombarding U-238 nuclei to release energy.
US tested in 1952, USSR did it in 1961.
Recently you must have seen this word making headlines all over the world.
Russia accused Ukraine of developing these and suddenly all attention drifted to this very word, ‘dirty bomb’.
Ukraine immediately invited officials from IAEA to inspect if they were really making one.
What is Dirty Bomb?
A dirty bomb is a device that releases large amount of radiation in short time intervals thereby inducing radiation sickness.
It does not target to kill by explosion rather by radiation sickness.
The maximum it can do is release more rems of radiation causing cancer particularly to those living in the vicinity of release of radioactive material.
If a radioactive material that decays releases 2 billion gamma rays for every cm2 it is called 1 rem. This is called radiation level. If you get 300 rems or more radiation level throughout the body you have a 50% chance you die out of radiation sickness. If you get 1000 rem or more you surely will due to radiation sickness. If you get more than 2500 rem or more you will have cancer.
Anti-Radiation Pills: Potassium Iodide
One common radioactive material that induces radiation sickness is radioactive Iodine (I-131) which is absorbed by thyroid gland in the neck.
Potassium Iodide is taken an anti-radiation pill which blocks thyroid from absorbing radioactive iodide.